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{{Short description|Dyes added to identify fuels}}
[[File:Red Diesel - geograph.org.uk - 339947.jpg|thumb|Plastic [[jerrycan]] containing 'red' diesel]]
'''Fuel dyes''' are [[dye]]s added to [[fuel]]s, as in some countries it is required by law to dye a low-tax fuel to deter its use in applications intended for higher-taxed ones. Untaxed fuels are referred to as "dyed", while taxed ones are called "clear" or "white".

[[Avgas|Aviation gasoline]] is dyed, both for tax reasons (avgas is typically taxed to support aviation infrastructure) as well as safety (due to the consequences of fuelling an aircraft with the wrong kind of fuel).

== Types of dyes ==
The dyes used have to be soluble in the fuels they are added to and therefore in [[hydrocarbon]]-based [[nonpolar]] solvents ("[[solvent dye]]s"). Red dyes are often various [[diazo dye]]s, e.g., [[Solvent Red 19]], [[Solvent Red 24]], and [[Solvent Red 26]]. [[Anthraquinone dyes]] are used for green and blue shades, e.g., Solvent Green 33, [[Solvent Blue 35]] and Solvent Blue 26.

The pure dyes found in modern liquid petroleum dyes are longer alkyl side chain forms of traditional dyes and normally multiple chain length variations of the [[chromophore]] are found within a typical commercial liquid petroleum dye.
For instance, Sudan Red 462 is a form of Solvent Red 19, with the ethyl side chain replaced by either a 2-ethylhexyl or a tridecyl side chain. The longer branched side chains improve solubility dramatically, but in some cases the high solubility prevents the dye being isolated as a crystal, except at very low temperatures.
The high-solubility liquid dyes originated with Morton International and BASF ([[ACNA (Italy)|ACNA Italy]]) as the primary inventors.
For instance, Morton International created Solvent Blue 98 as a high solubility form of Solvent Blue 35. BASF created Solvent Blue 79 as its high solubility form of Solvent Blue 35.
In some cases it is possible, with normal solvents—e.g., xylene—to prepare stable (to -20C) solutions at 65% "solids" content. The original powder dye form of the chromophore would not be soluble beyond 2% in xylene.

Only a few [[Refinery|refineries]] worldwide still use powder dyes for colouring fuels, as although they are lower cost per active molecule of dye chromophore than the modified forms, they have significant handling issues and health and safety issues that inherently arise from the handling of [[azo dye]]s (reds/yellows/green mixes). It is advantageous to mix a liquid with a liquid instead of handling powdered dyes into a liquid.

==Fuel dye in Europe==
{{More citations needed section|date=July 2010}}
[[File:Petrol_pump,_Aherlow.jpg|thumb|Fuel pumps in Ireland, with green [[gas oil]] and red [[kerosene]], and notices that it is an offence to use marked fuels in a motor vehicle]]
After August 2002, all [[European Union]] countries became obliged to add about {{cvt|6|mg/L|oz/oilbbl}} of [[Solvent Yellow 124]], a dye with structure similar to [[Solvent Yellow 56]], to heating fuel. This dye can be easily hydrolyzed with acids, splitting off the [[acetal]] group responsible for its solubility in nonpolar solvents, and yielding a water-soluble form. Like a similar [[methyl orange]] dye, it changes color to red in acidic pH. It can be easily detected in the fuel at levels as low as 0.3 ppm by extraction to a diluted [[hydrochloric acid]], allowing detection of the red diesel added into motor diesel in amounts as low as 2–3%.
With the implementation decision (EU) 2022/197 by the European Commission, ACCUTRACE Plus, developed by [[Dow Chemical Company]], replaced the Euromarker [[Solvent Yellow 124]] dye on January 18, 2024. The new Accutrace dye is significantly more difficult to remove from [[gas oil]] than its predecessor. Consequently, the introduction of this new fuel dye is expected to reduce the illegal conversion of gas oil, subject to reduced taxation, into [[diesel fuel]].<ref name="EUDEC" >{{Cite web|url=http://data.europa.eu/eli/dec_impl/2022/197/oj|title=Commission Implementing Decision (EU) 2022/197 of 17 January 2022 establishing a common fiscal marker for gas oils and kerosene (notified under document C(2022) 74)|date=2022-01-17|access-date=2024-01-04|language=en}}</ref><ref>{{cite web | url=https://op.europa.eu/en/publication-detail/-/publication/59070558-8d38-11ec-8c40-01aa75ed71a1/language-en/format-PDFA2A | title=C/2022/74, Commission Implementing Decision (EU) 2022/197 of 17 January 2022 establishing a common fiscal marker for gas oils and kerosene (Notified under document C(2022) 74) | date=17 January 2022 }}</ref> Accutrace can be detected in trace amounts using [[gas chromatography]], both in laboratory and field settings.<ref>{{Cite web|url=https://www.dow.com/en-us/brand/accutrace.html|title=ACCUTRACE™|website=www.dow.com|access-date=2024-01-04|language=en-US}}</ref> Residues from both Accutrace and the previous Euromarker dyes persist in fuel tanks and filters long after the illegal gas oil has been discontinued. Thus, even months after switching to legitimate diesel fuel, traces of illegal gas oil use can still be identified.

===United Kingdom{{anchor|red diesel}}===
{{Infobox UK legislation
| short_title           = Motor Spirit (Regulation) Act 1948
| type                  = Act
| parliament            = Parliament of the United Kingdom
| long_title            = An Act to create certain offences in connection with the supply and use of motor spirit, and for purposes connected therewith.
| year                  = 1948
| citation              = [[11 & 12 Geo. 6]]. c. 34
| introduced_commons    = 
| introduced_lords      = 
| territorial_extent    = 
| royal_assent          = 28 May 1948
| commencement          = 
| expiry_date           = 
| repeal_date           = 
| amends                = 
| replaces              = 
| amendments            = 
| repealing_legislation = 
| related_legislation   = 
| status                = 
| legislation_history   = 
| theyworkforyou        = 
| millbankhansard       = 
| original_text         = 
| revised_text          = 
| use_new_UK-LEG        = 
| UK-LEG_title          = 
| collapsed             = yes
}}
[[File:Station Road Garage - prices - geograph.org.uk - 847101.jpg|thumb|[[Petrol station]] in England, with 'red diesel' available for a lower price, but only for "off road use", i.e. agricultural machinery and similar]]
In the [[United Kingdom]], "red diesel" is dyed gas oil for registered agricultural or construction vehicles such as tractors, excavators, cranes and some other [[Non-road engine|non-road applications]] such as boats. Red diesel carries a significantly reduced tax levy compared to un-dyed diesel fuel used in ordinary road vehicles. As red diesel is widely available in the UK, the authorities regularly carry out roadside checks. Unauthorised use incurs heavy fines but despite this, spot checks have occasionally found as many as one in five motorists using red diesel.<ref name="BBC1" >{{cite web| title=Thousands using illegal car fuel|url=http://news.bbc.co.uk/1/hi/uk/7076799.stm|work=BBC News|date=2007-11-03|access-date=2008-04-16}}</ref>

Red diesel can also be used in road vehicles which are [[SORN|registered as off-road with the DVLA]] provided they are only used on private land. On 14 July 2014, the European Commission announced it was referring the United Kingdom to the European Court of Justice over the use of red diesel in propelling private pleasure craft on water. It believed the UK was not properly applying EU regulations for the fiscal marking of fuels.<ref name="RYA" >{{cite web
|url= http://www.rya.org.uk/newsevents/news/Pages/ECtotakeUKtocourtoverreddiesel.aspx|title=EC to take UK to court over red diesel|work=[[Royal Yachting Association]]|date=2014-07-14|access-date=2014-08-01}}</ref>

On 18 November 2014, a new measure to combat fuel laundering was set to result in the illegal trade being "virtually eliminated" in the United Kingdom, according to [[HM Revenue and Customs]]. A new dye was introduced in April 2015 in the United Kingdom and the [[Republic of Ireland]].<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-northern-ireland-30104476|title=HMRC: New diesel dye 'should eliminate fuel laundering'|publisher=BBC News|date=18 November 2014}}</ref>

====Carbon offset red diesel====
In 2014, Crown Oil became the first fuel supplier to begin offering their red diesel customers the opportunity to purchase [[carbon offset]] red diesel which is marketed as a more environmentally friendly alternative. With the additional costs incurred being used to purchase carbon credits, with projects aimed at lowering carbon emissions around the world, offering businesses a more sustainable way to use red diesel.<ref name="Crown Oil" >{{cite web| title=Carbon Offset Red Diesel|url=https://www.crownoil.co.uk/products/carbon-offset-red-diesel/|work=Crown Oil Ltd|date=2014}}</ref>

=== Finland ===
[[File:Diesel-Motoroil Pump.jpg|thumb|Diesel (black) and dyed fuel oil (MPÖ; red) dispensers at a [[St1]] petrol station in Tornio, Finland]]
Low-tax dyed fuel oil ({{langx|fi|polttoöljy}}; {{langx|sv|brännolja}}; always abbreviated on nozzles as ''MPÖ'') is available in many rural petrol stations in Finland, primarily intended for certain types of non-road vehicles such as tractors and driveable construction vehicles. Until 2002, [[furfural]] was used to dye fuel oil in Finland, when it was replaced with Solvent Yellow 124. Since 2008, boats and pleasure craft are no longer legally allowed to use low-tax fuel oil; instead, taxable diesel must be used for fuel.

=== Poland ===
Currently there are no naked-eye visible dyes in car fuels sold in Poland. Previously, during the time of [[Polish United Workers' Party|Communist Party rule]], the state-owned [[Orlen|CPN]] fuel monopoly dyed leaded gasolines (marketed as "ethilins") in the following colors: 78 – blue, 86 – green, 94 – yellow, 98 – red. Diesel fuel, although unleaded, was also dyed a brown color.

==Fuel dye in North America==
In the [[United States of America]], the [[United States Environmental Protection Agency|Environmental Protection Agency]] mandates use of a red dye to identify fuels for off-road use. [[Solvent Red 26]] is used in the United States as a standard, though it is often replaced with [[Solvent Red 164]], which is similar to Solvent Red 26 but with longer [[alkyl]] chains. The [[Internal Revenue Service]] regulation {{CodeFedReg|26|48|4082-1}} mandates use of the same red dyes, in fivefold concentration, for tax-exempt diesel fuels such as [[heating oil]]; their argument for the higher dye content is to allow detection even when diluted with "legal" fuel. Detection of red-dyed fuel in the fuel system of an on-road vehicle will incur substantial penalties.

==Fuel laundering==
{{anchor|Laundering}}<!-- [[Fuel laundering]] and [[Diesel laundering]] redirect here -->
[[Organised crime]] gangs may "launder" low-price dyed fuel, removing the dye and selling it illegally to unsuspecting motorists at the higher price of undyed fuel. Paramilitary groups connected to [[The Troubles|political unrest in Northern Ireland]] have established laundering plants on both sides of the [[Irish border]]. In 2004, Northern Irish police discovered an illegal facility capable of removing the dye from {{convert|12|e6L|e6impgal e6usgal|abbr=unit}} per year.<ref name="BBC2" >{{cite web  | title = Blackmarket Britain: Fake Fuel  | url=http://news.bbc.co.uk/1/hi/business/3086941.stm  | access-date = 2008-04-16  | work=BBC News | date=2004-06-09}}</ref> In 2009, customs officials shut down a plant capable of removing the dye from  6.5 million litres of fuel per year.<ref>{{cite web  | title = Illegal fuel plant largest in NI  | url=http://news.bbc.co.uk/1/hi/northern_ireland/8389523.stm  | access-date = 2009-12-01  | work=BBC News | date=2009-12-01}}
</ref> In 2011, a plant capable of processing 30 million litres was discovered.<ref>{{cite web  | title = UK's biggest fuel laundering plant found in Crossmaglen  | url=https://www.bbc.co.uk/news/uk-northern-ireland-12757309  | access-date = 2011-03-17  | work=BBC News | date=2011-03-16}}</ref> The European Union aims to combat fuel laundering with the introduction of the new fuel dye Accutrace starting from 2024.<ref name="EUDEC" />

==Fuel theft==
Fuel is being dyed by companies such as [[Bord na Móna]] in Ireland in an effort to combat the widespread theft of fuel.<ref>{{cite news| title=Bord na Móna to dye fuel to fight theft | url=http://www.irishtimes.com/news/bord-na-m%C3%B3na-to-dye-fuel-to-fight-theft-1.2179 | access-date = 2015-06-06 | newspaper=[[Irish Times]] | date=2012-12-11  }}</ref>

==Dyes used by country==
Some dyes required in some countries are listed here:

{| class="wikitable"
|+
|-
! Country
! Fuel
! Dye
|-
| rowspan="2" | {{AUS}}
| Regular unleaded [[petrol]]
| undyed – clear to yellow (was purple or brown up to 2013, was red/orange until 2015)<ref>{{cite press release | title=The colour of Australian unleaded petrol is changing to red/orange | url=http://www.aip.com.au/topics/mr_pdf/AIP_media_release_280912.pdf | access-date=2012-11-22 | publisher=[[Australian Institute of Petroleum]] | date=2012-09-28 | url-status=dead | archive-url=https://web.archive.org/web/20130409211243/http://www.aip.com.au/topics/mr_pdf/AIP_media_release_280912.pdf | archive-date=2013-04-09 }}</ref><ref name="AIP2015">{{cite web |title=The Colour of Australian Unleaded Petrol is Changing |url=https://aip.com.au/sites/default/files/download-files/2017-09/AIP_ULP_Colour_Press_Release_and_QA.pdf |publisher=[[Australian Institute of Petroleum]] |access-date=28 March 2020}}</ref>
|-
| Premium unleaded [[petrol]]
| undyed – clear to yellow<ref name="AIP2015" />
|-
| {{AUT}}
| [[Heating oil]]
| any red dye and [[Solvent Yellow 124]]
|-
| rowspan="3" |{{CAN}}
| Off-road fuel (agriculture, construction, mining etc.)
| red/purple dye
|-
|Marine gasoline
|any red dye
|-
| Heating oil
| any red dye
|- 0
| rowspan="2" | {{FIN}}
| [[Heating oil]]
| [[Solvent Yellow 124]]
|-
| Diesel for construction and agriculture
| [[Solvent Yellow 124]]
|-
| rowspan="3" | {{FRA}}
| [[Diesel fuel|Diesel]] (off-road)
| [[Solvent Red 24]] and [[Solvent Yellow 124]]<ref>{{Cite web |url=https://www.legifrance.gouv.fr/loda/article_lc/LEGIARTI000043973310|title=Article 3 - Arrêté du 10 novembre 2011 fixant pour le gazole, les gaz de pétrole liquéfiés et les émulsions d'eau dans du gazole des conditions d'emploi ouvrant droit à l'application du régime fiscal privilégié institué par l'article 265 du code des douanes en matière de taxe intérieure de consommation|date=30 June 2021|access-date=29 January 2023}}</ref>
|-
| [[Heating oil]]
| [[Solvent Red 24]] and [[Solvent Yellow 124]]<ref>{{Cite web |url=https://www.legifrance.gouv.fr/loda/article_lc/LEGIARTI000023401687|title=Article 2 - Arrêté du 15 juillet 2010 relatif aux caractéristiques du fioul domestique|date=10 December 2010|access-date=29 January 2023}}</ref>
|-
| [[Kerosene]] as heating fuel
| [[Solvent Yellow 124]]<ref>{{Cite web |url=https://www.legifrance.gouv.fr/loda/article_lc/LEGIARTI000006213415|title=Article 3 - Arrêté du 18 juillet 2002 fixant pour le white-spirit et le pétrole lampant utilisés comme combustible de chauffage les conditions d'emploi ouvrant droit à l'application du régime fiscal privilégié institué par l'article 265 (tableau B) du code des douanes en matière de taxe intérieure de consommation et fixant les mesures auxquelles doivent se conformer les importateurs et les distributeurs desdits produits|date=18 July 2002|access-date=29 January 2023}}</ref>
|-
| Marine [[Diesel fuel|diesel]]
| [[Solvent Blue 35]]
|-
| rowspan="3" |{{LAT}}
|
| [[Solvent Yellow 124]]. SIA "Straujupīte" for diesel labeling is using no more than 0.2% of sulfur content.<ref>{{Cite web |url=http://www.straujupite.lv/en/fuel/marked-fuel/ |title=Marked fuel - Straujupite.lv - degvielas vairumtirdzniecība |access-date=2 April 2017 |archive-date=3 April 2017 |archive-url=https://web.archive.org/web/20170403025236/http://www.straujupite.lv/en/fuel/marked-fuel/ |url-status=dead }}</ref>

Diesel is labeled  by adding one of the coloring matters to 1000 liters of oil products:
* (N-ethyl-1- (4-fenilazofenilazo) naphthyl-2-amine – at least 5.0 grams;
|-
| rowspan="2" | Agricultural diesel<ref>{{Cite web |url=http://www.straujupite.lv/en/fuel/agro-fuel/ |title=Agro fuel - Straujupite.lv - degvielas vairumtirdzniecība |access-date=2 April 2017 |archive-date=3 April 2017 |archive-url=https://web.archive.org/web/20170403025238/http://www.straujupite.lv/en/fuel/agro-fuel/ |url-status=dead }}</ref>
|fiscal marker – Solvent Yellow 124, CAS Nr.34432-92-3 – at least 6.0 grams, and no more than 9.0 grams, per 1000&nbsp;L
|-
|Solvent Blue 35, CAS no. 17354-14-2, or any other equivalent blue coloring – at least 7.0 grams per 1000&nbsp;L<ref>{{Cite web|url=https://likumi.lv/ta/id/81066-par-akcizes-nodokli|title=Par akcīzes nodokli|website=Likumi.lv|language=lv|access-date=2017-04-02}}</ref>
|-
| rowspan="2" | {{EST}}
| [[Heating oil]]
| Automate Red NR or similar
|-
| Agricultural diesel
| Automate Blue 8 GHF or similar
|-
| rowspan="1" |{{GER}}
| [[Heating oil]]
| [[Solvent Yellow 124]] + 4.1 gr/litre Solvent Red 19 or 5.3 gr tolyazotolyazo-ethylhexylbetanaphthylamine or 6.1 gr  tolyazotolyazo-tridecylbetanaphthylamine and similar
|-
| rowspan="2" | {{GRE}}
| [[Heating oil]]
| any red dye
|-
| Marine diesel
| any black dye
|-
| {{HUN}}
| [[Heating oil]]
| [[Ferrocene]]
|-
| {{IND}}
| Subsidised [[Kerosene]]
| Blue dye
|-
| rowspan="3" |{{INA}}
| Pertalite (RON 90)
| Green dye
|-
| PERTAMAX (RON 92)
| Blue dye
|-
| PERTAMAX Turbo (RON 98)
| Red dye
|-
| rowspan="2" | {{IRL}}
| Gas oil
| green dye = [[Solvent Yellow 124]] and Anthraquinone Blue dye equivalent to [[Solvent Blue 35]] and ACCUTRACE S10 ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene]]<ref name="tax-news">{{cite web|url=https://www.tax-news.com/news/Ireland_To_Use_New_Marker_For_Lower_Duty_Fuels____66766.html|archive-url=https://web.archive.org/web/20150330210129/http://www.tax-news.com/news/Ireland_To_Use_New_Marker_For_Lower_Duty_Fuels____66766.html|url-status=usurped|archive-date=30 March 2015|title=Ireland To Use New Marker For Lower Duty Fuels|first=Jason|last=Gorringe|website=Tax-News.com|date=22 December 2014}}</ref>
|-
| [[Kerosene]]
| [[Solvent Red 19]], Solvent Yellow 124 and ACCUTRACE S10 ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene<ref name="tax-news"/>
|-
| rowspan="2" | {{ITA}}
| Heating oil
| Solvent Red 161
|-
| Gas oil
| Solvent Green 32 or 33 and [[Solvent Yellow 124]]
|-
| {{NED}}
| Agricultural diesel
| any red dye and [[Solvent Yellow 124]] (the additive [[Furfural]] is obsolete)
|-
| {{NOR}}
| Agricultural diesel
| any green dye
|-
| rowspan="2" | {{POR}}
| Agricultural diesel
| [[Solvent Blue 35]]
|-
| Heating oil
| [[Solvent Red 19]] and similar
|-
| rowspan="2" | {{ESP}}
| Agricultural diesel
| any red dye + Solvent Yellow 124: Orden PRE/1724/2002 of 5 July.
|-
| Heating oil
| any blue dye + Solvent Yellow 124: Orden PRE/1724/2002 of 5 July.
|-
| {{SWE}}
| Heating oil
| [[Solvent Blue 35]], Solvent Blue 79, Solvent Blue 98 and [[Solvent Yellow 124]]
|-
| rowspan="2" |{{THA}}
| Gasoline 95
| yellow dye
|-
| Gasoline 91
| red dye
|-
| rowspan="2" | {{GBR}}
| [[Gas oil]] ("red diesel")
| [[Solvent Red 24]], [[quinizarin]], [[Solvent Yellow 124]] and ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene<ref name="uk-fuel-marker">{{cite web|url=https://www.gov.uk/government/publications/revenue-and-customs-brief-4-2015-introduction-of-a-new-rebated-fuel-marker-from-1-april-2015/revenue-and-customs-brief-4-2015-introduction-of-a-new-rebated-fuel-marker-from-1-april-2015|title=Revenue and Customs Brief 4 (2015): introduction of a new rebated fuel marker from 1 April 2015|website=Gov.uk}}</ref>
|-
| Rebated [[kerosene]]
| [[Coumarin]], [[Solvent Yellow 124]] and ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene<ref name="uk-fuel-marker"/>
|-
| {{EUR}}
| many rebated
| [[Solvent Yellow 124]] ("Euromarker") Transition commenced to replace this by ButoxyBenzene from 18 January 2024
|-
| {{USA}}
| low-tax fuels, high-sulfur fuels
| [[Solvent Red 26]] 3.9&nbsp;lbs per 1000 barrels ({{convert|0.0039|lb/oilbbl|mg/L|disp=out}}), [[Solvent Red 164]]
|-
| rowspan="4" | Worldwide
| Aviation gasoline 80/87
| red dye
|-
| Aviation gasoline 82UL
| purple dye
|-
| Aviation gasoline 100LL
| blue dye
|-
| Aviation gasoline 100/130
| green dye
|}

== See also ==
* [[Denatured alcohol]]

==References==
{{Reflist}}

==External links==
* [http://www.dps.state.mn.us/patrol/comveh/dyedfuel/index.htm Minnesota State Patrol Commercial Vehicle Enforcement Dyed Fuel Program] {{Webarchive|url=https://web.archive.org/web/20061212063207/http://www.dps.state.mn.us/patrol/comveh/dyedfuel/index.htm |date=12 December 2006 }}
* [https://web.archive.org/web/20080714154427/http://www.shell.com/home/content/aviation-en/productservice/aviationfuels/detail/avgasgradesspecs_10081006.html Shell information on aviation gasoline specifications]
* [https://www.crownoil.co.uk Crown Oil fuel dye information]
{{Use dmy dates|date=February 2020}}

[[Category:Fuel dyes| ]]